Flexural Behavior and Design of Rc Members Using FRP Reinforcement

Flexural design for concrete members reinforced with fiber-reinforced-plastic (FRP) composites may be conducted using both the ultimate-strength method and the working-stress method. Since FRP reinforcement does not yield, there should be the explicit provision that failure be controlled by concrete crushing as opposed to reinforcement rupture. Deflection control may become as important as flexural strength for the design of FRP-reinforced concrete structures. The paper contends that, at this stage of development, the working-stress method is better suited to FRP-reinforced concrete. The primary reasons are that the predicted ultimate moment capacity represents a highly variable state only attainable at a high level of deformation and crack opening and that it depends strictly on concrete ultimate strain. FRP reinforcement is better suited to pre- and posttensioned-type concrete members; however, it cannot be ruled out that FRP should become the reinforcement of choice in special nonprestressed applications where durability or magnetic permeability are the controlling parameters.